September 6, 2018

AIVR/VT or Aberrancy?

Pt admitted due to SOB due to CHF. Is this accelerated idioventricular rhythm/ventricular tachycardia (AIVR/VT) or aberrancy?

In patients with baseline sinus rhythm, it is easy to identify VT from aberrancy. There are 3 basic rules. First, when the run of WCT is preceded by a premature P wave (often the P wave has a different morphology), then it is SVT with aberrant conduction.  Second, if the WCT is preceded by a regularly (not prematurely) occurring sinus P wave (the PR interval is shorter than that of normally conducted sinus beats), it is ventricular tachycardia. Third, if the WCT is not preceded by a P wave, it is ventricular tachycardia. In this case, there is a regular sinus P wave (red arrow) with a PR shorter than that during normally conducted sinus beats. So, this is an IAVR/VT.

The second evidence for interpreting this wide QRS rhythm is AIVR/VT is the presence of fusion beats (black arrows) on the bottom strip. The morphology of those 2 beats are INTERMEDIATE between sinus beats and ventricular ectopic beats. This means that the ventricles are depolarized both by the ectopic ventricular impulse and a supraventricular impulse (sinus beat).

The third evidence that this is VT is the presence of R>R' or the "rabbit ear" sign in the V lead.

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